1. Field of the Invention
The present invention relates to a measuring technique of the earth""s natural magnetism, and it particularly relates to a terrestrial magnetism detecting sensor which corrects the error encountered in azimuth calculation, and also relates to an azimuth measuring method thereof.
2. Description of the Related Art
The terrestrial magnetism detecting sensor is utilized to measure the orientation of an observation spot. The terrestrial magnetism detecting sensor also simply referred to as a magnetic sensor or a terrestrial magnetic sensor is placed on a horizontal plane at the observation spot, and detects biaxial or two-axis components of a terrestrial magnetic vector in the horizontal plane. The magnetic bearing is calculated based on the two axis components detected by the terrestrial magnetism detecting sensor. The terrestrial magnetism detecting sensor is used in the navigation system employed in an automobile, and is put on the market after certain calibration procedure has been performed to correct the magnetic effect.
On the other hand, it is widely prevalent that the map data are displayed in the cellular phone and other mobile terminals. In the light of this current situation, the applicant of the present invention first propose that the terrestrial magnetic sensor be built into portable equipment such as the cellular phone and mobile terminal, and came to recognize the following objects in the course of examining the realization of his proposal. Namely, the portable equipment may be held at any position depending on the posture of an owner of the portable equipment or how it is held by the owner, so that the direction of the portable equipment is not stabilized and constantly changes. Thus, the terrestrial magnetic sensor equipped in the portable equipment may be inclined by any possible tilt angle with respect to the horizontal position, and its tilt angle may constantly fluctuate. Therefore, under such a usage environment, besides the removal of the static magnetic effect as described above, an effect due to the change of the posture and holding position need be eliminated so that detection signals of the terrestrial magnetic vector can be automatically corrected.
The present invention has been made by the applicant in recognition of the above and an object thereof is to provide a compact-size terrestrial magnetic sensor capable of automatically correcting inclination, and an azimuth measuring method utilizing the terrestrial magnetic sensor.
In Japanese Patent Application No. 2000-104689, the applicant of the present invention proposed a portable terminal equipment to which a two-axis magnetic sensor is built in, and proposed a position data display system which can process a map according to the orientation of the map displayed in the portable terminal equipment. Moreover, the applicant of the present invention herewith proposes an omnidirectional magnetic sensor which incorporates a tilt sensor or inclination sensor into a magnetic sensor and which is capable of automatically correcting the inclination in order to improve usability of the system.
According to an aspect of the present invention relating to a three axis magnetic sensor, the three axis magnetic sensor is so structured that the two axis magnetic sensor and a magnetism detecting element are integrally structured as a hybrid IC. The two axis magnetic sensor is so formed that a base serves as a main member and detects two axial components specified by a plane parallel to the base. The magnetic detecting element detects a component of a direction orthogonal to the plane. Thereby, the three axis magnetic sensor can detect three axial component of the magnetic vector of the terrestrial magnetism. As the magnetism detecting element, a magnetic induction element such as a Hall element which detects magnetism by the Hall effect may be used, or a magneto-resistance effect element such as an MR (magnetoresistive) element which detects the magnetism by a phenomenon in which an electric resistance varies relative to magnetization of ferromagnetic body may be used.
The two axis magnetic sensor may be structured such that a coil pattern for detecting the two axis components of the magnetic vector is formed on a stacked base. The two axis magnetic sensor may be a flux gate type magnetic sensor in which an amorphous ring coil serves as a core, and a first coil base for detecting a magnetic field component in the X axis of a plane parallel to the base and a second coil base for detecting a magnetic field component in the Y axis of the plane are stacked on the outer surface of an exciting coil base.
As a mounting embodiment in which the two axis magnetic sensor and the magnetism detecting element are integrally structured together, the base on which the two axis magnetic sensor is formed may include a pattern for transmitting a detection signal outputted from the magnetism detecting element, so that the detection signal may be directly introduced into the base via the pattern when the magnetism detecting element is mounted on the base.
According to another aspect of the present invention relating to an omnidirectional magnetic sensor, the omnidirectional magnetic sensor is structured such that a three axis magnetic sensor for detecting a three dimensional magnetic vector and a tilt sensor for detecting a tilt angle of the base are integrally formed together. xe2x80x9cBeing formed on the basexe2x80x9d indicates, for example, that at least part of a structural component of the three axis magnetic sensor is so formed that the base serves as a main member, and it includes cases where other structural components of the three axis magnetic sensor is mounted outside the base and where all structural components of the three axis magnetic sensor are so formed that the base serves as the main member. For example, the two axis magnetic sensor which detects two axis components of a magnetic vector specified by a plane parallel to the base, may be formed with the base as the main member, while a magnetism detecting element which detects a component in a direction vertical to the plane of the magnetic vector may be so mounted that the magnetism detecting element is connected to a pattern formed on the base.
The tilt sensor may detect a tilt angle in the X axis and a tilt angle in the Y axis specified by a plane parallel to the base. The tilt sensor may be an acceleration sensor which detects displacement in the two axis direction or the three axis direction.
The base may include a pattern which transfers a detection signal outputted from the tilt sensor, so that the detection signal may be directly introduced to the base via the pattern when the tilt sensor is mounted on the base.
The omnidirectional magnetic sensor as recited may further comprise a film base mounted on the base in the form externally extended from the base, where the tilt sensor is mounted on the film base, the film base is folded toward the base, and whole members including the tilt sensor are fixed.
Moreover, the three axis magnetic sensor may be so formed that the base servers as a main member, and the three axis magnetic sensor may include a two axis magnetic sensor which detects two axis components of a magnetic vector defined by a plane parallel to the base, and a magnetism detecting element which detects a component corresponding to a direction orthogonal to the plane of the magnetic vector. The magnetism detecting element may be mounted on the film base. A flip chip method may be utilized to mount the element on the film.
According to still another aspect of the present invention relating to an azimuth measuring method, the azimuth measuring method includes the steps of: receiving a signal of a three-dimensional magnetic vector detected by a magnetic sensor; receiving inclination formed between three dimensional coordinates specified by the magnetic vector and a horizontal plane, from a tilt sensor; and calculating a magnetic vector which ought to be detected when the magnetic sensor is placed horizontal to the horizontal plane, based on the magnetic vector detected by the magnetic sensor and the inclination detected by the tilt sensor. Moreover, the azimuth measuring method may further include the step of calculating magnetic declination based on the calculated magnetic vector.
Moreover, any arbitrary combination of the above-mentioned structural components in the present invention is still effective as an embodiment when applied as a method, a sensor, and a system and so forth.
Moreover, this summary of the invention does not necessarily describe all necessarily features so that the invention may also be sub-combination of these described features.